Green Party members will decide at their conference in October whether to join the Yes Scotland campaign.

If they decide to withdraw their support, it will mean that the “cross-party” campaign will consist only of the SNP and the far-left Scottish Socialist Party.

Not even a fortnight in, and the Yes Scotland campaign is already falling apart

Scottish Conservative leader Ruth Davidson

Mr Harvie, a Glasgow MSP, said: “We feel frustrated by the lack of progress towards a genuinely inclusive campaign, and concerned that a non-inclusive campaign will be less likely to succeed. If we are to formally sign up as a party we need to know on what terms.

“We don’t want to end up simply cheerleading for the SNP. It’s entirely possible the membership takes the view that Greens help shape another pro-independence referendum campaign.”

The Greens are not Nationalists, but want to use independence to push their policies such as abolishing the monarchy, nuclear disarmament and renewable energy.

Supporters at the event, staged in an Edinburgh cinema, signed a “Yes declaration” stating it is “fundamentally better” if decisions about the country’s future are taken by the people of Scotland. The aim is to have one million voters to sign it before the referendum.

Last night Labour culture and external affairs spokeswoman Patricia Ferguson said: “This is chaotic. The Nationalist campaign has barely lasted three weeks and things have gone from bad to worse.

"It looks like Patrick Harvie shares an experience many in the SNP have found – it is Alex Salmond’s way or the highway. Alex Salmond sees the referendum as his personal plaything. After all, there was a clue at the launch – the cinema was showing The Dictator.”

“It is clear the cross-party support Alex Salmond claimed for his separatist movement was nothing more than window dressing.”

The launch of the Yes Scotland campaign last month included famous faces such as Bourne Identity star Brian Cox, X-Men actor Alan Cumming and Martin Compston of Sweet Sixteen fame.

A Yes Scotland spokesman said: “Many individual Greens are already making a real contribution to Yes Scotland and we look forward to the Green Party conference deciding to work formally within Yes Scotland or in parallel towards a Yes vote.”